docs: def read_identifiables(self, cls,  sdmxobj, offset=None):
          '''
          If sdmxobj inherits from dict: update it  with modelized elements.
          These must be instances of model.IdentifiableArtefact,
          i.e. have an 'id' attribute. This will be used as dict keys.
          If sdmxobj does not inherit from dict: return a new DictLike.
          '''
          path = self._paths[cls]
          if offset:
              try:
                  base = self._paths[offset](sdmxobj._elem)[0]
              except IndexError:
                  return None
          else:
              base = sdmxobj._elem
          result = {e.get('id'): cls(self, e) for e in path(base)}
          if isinstance(sdmxobj, dict):
              sdmxobj.update(result)
          else:
              return DictLike(result)